Stroop (1938) found that subjects required considerably more time to name colors when the colors were presented in the names of conflicting colors. For example, if the word BLUE was printed in green ink, identifying the ink color (green) took more time than identifying the ink color if the word was consistent (GREEN). As a result, the Stroop effect has been defined as the interference that occurs when processing one dimension of a complex stimulus while ignoring other dimensions. There are few psychological phenomena that have received as much empirical research attention as the Stroop effect. In fact, MacLeod (1991) provided an integrative review of over 50 years of research on the Stroop effect. Studies have investigated the causes of the effect (Dyer, 1971a; Hintzman, Capre, Eskridge, Owens, Shaff, & Sparks, 1972; Nealis, 1973; Wheeler, 1977) the differential effects across various groups (Das, 1970; Dyer, 1971b; Golden, 1974) and the multiple uses of a Stroop test in diagnostic settings (Dyer, 1973; Golden, 1976).

Theoretical Explanations

The Stroop effect is hypothesized to result from several cognitive and physiological factors. Nealis (1973) and Wheeler (1977) proposed that the Stroop effect occurs as a result of the interference that occurs when two possible responses compete. In Stroop scenarios, participants are shown stimuli that may contain one or two sets of information to process. When a complex stimulus (i.e., one containing both verbal and color information) is displayed, participants must attend to and identify one dimension of the stimulus while ignoring the other dimension. When such selective attention is required, some stimuli provide greater interference than others do. Previous studies have suggested that reading is a relatively automatic process. If reading does occur automatically, verbal material may provide more interference because of the difficulty in ignoring it.

A potential physiological explanation for the Stroop effect is related to the lateralization of certain cognitive functions to different hemispheres of the brain. In Stroop scenarios, the stimuli presented may contain both verbal and color information. Research on hemispheric specialization has supported the notion that verbal functions (including language, speech, and writing) tend to be localized in the left hemisphere and non-verbal functions (spatial problems, music, art, and color distinction) tend to be localized in the right hemisphere (Corballis, 1991). If an identification task involves functions tapping both hemispheres, it is more cognitively complex and thus requires more time to process.

Tests and Applications

The Stroop effect has been found to affect various demographic groups differently. Das (1970) studied changes in Stroop test responses as a function of mental age and Dyer (1971) studied differences in monolinguals and bilinguals. Golden (1974) investigated gender differences and found females’ performance on color-identification trials to be faster than males. However, measures of interference were not significantly across gender groups.

The Stroop test has also been used for diagnostic purposes. Dyer (1973) outlined how the Stroop phenomenon has been used to study various perceptual and cognitive processes. Golden (1976) also discussed how the Stroop test has been used to diagnose brain damage.

The Present Study

Although the Stroop effect has been studied extensively, questions remain. The intent of this study is to ......